code: def _initialize_resolver_default_dict():
      return collections.defaultdict(
          lambda: collections.defaultdict(list)
      )
  
file_path: ml-metadata/ml_metadata/tools/mlmd_resolver/metadata_resolver_utils.py
imports: import collections
  import enum
  from typing import Callable, Dict, List, Optional, Set
  import attr
  from ml_metadata.proto import metadata_store_pb2
label_desc: Use image node_id 1 for calling a global function with example usage: _initialize_resolver_default_dict() and returns: collections